Guide blades in low-pressure turbines of turbomachines are frequently situated successively in multiple rows in a device referred to as a drum, which are fixedly connected on the outer circumference side to a housing section of the low-pressure turbine. The guide blades of one row are preferably combined into guide blade groups, so that multiple guide blades may be simultaneously positioned in the drum. For positioning on the inner circumference side, the drum has a plurality of uniformly distributed receptacles on the inner circumference side for accommodating holding elements of the guide blade groups. The receptacles are conventionally axial grooves, and the holding elements are radially outer axial ribs. To reduce the weight and to optimize the device or the drum from a structural mechanical point of view, a plurality of recesses situated on the inner circumference side, so-called “scallops,” are conventionally provided between the axial grooves. However, the recesses favor malpositioning of the guide blade group in the circumferential direction, since these may immerse with their holding elements or ribs into the recesses, and thus a setpoint position of the guide blade groups is feigned. However, during operation an undetected faulty position results in considerable damage in the turbomachine.